The bad news: George R.R. Martin really wants to put Bran Stark on the throne — and that's exactly what he'll do in the books. The good news: it won't look as ridiculous in A Song of Ice and Fire as it did in Game of Thrones season 8. Because Martin's Bran is a completely different character, and his path to power is much deeper and more logical.
Actor Isaac Hempstead-Wright himself said that Martin had outlined two key points for Bran in advance: the scene with Hodor and the crown. That is, Bran was always the "final king" in the author's version. It's just that the show missed the most important thing — the formation of the hero.
While the series was hastily wrapping up plots and resetting characters, the book Bran is slowly learning to be the new "three-eyed raven" under the supervision of the old one — a loyal servant of the Targaryens, a former Hand and a participant in political intrigue even before Daenerys.
And one more thing — there is no Night King in the books. Physically. There are ancient legends, there are hints, but a large-scale fantasy battle with a blue-eyed villain is a showrunner's invention.
Martin's main conflict is not a battle, but a choice: who will lead Westeros forward? And here Bran is the ideal option: he does not thirst for power, but sees the past, understands the present and feels the future. He is a neutral observer, ready to become a wise arbiter.
So the ending will remain the same, but with a different weight. The main thing is to wait for The Winds of Winter, there we will get all the answers. But, alas, the wait may take more than one winter.